As constructed, the Celtics will face teams with more talent almost every night. Their best chance to win is to play excellent defense, excellent offense, excellent everything, with the other team making enough mistakes to hurt its own chances.

But if the Celtics’ foes play well — or at least up to their talent level — and the Celtics don’t respond with an all-around awesomeness, then a Boston loss is all but assured, at least while All-Star point guard Rajon Rondo (knee) is sidelined.

That’s just how it will be for this rebuilding team this season, and that reality played out Friday night at TD Garden, where a better, more talented Portland Trail Blazers team played up to its abilities and soundly defeated the Celtics, 109-96.

“Yeah, you can’t outscore those guys,” Celtics coach Brad Stevens said. “You’re going to have to defend them, and I thought we didn’t do that very well.”

It was the Celtics’ second straight loss and the fifth straight win for the Trail Blazers (7-2). It’s also Portland’s first win in Boston since 2004, snapping a nine-game losing skid.

The Celtics have allowed 105 or more points in three of their last four games, winning two of them.

“If you want to win basketball games in this league, you have to play defense. Period, point-blank,” Sullinger said. “If you’re not playing defense, you might as well count on losing. We’ve got a lot of work to do.”

The Celtics played with effort, but that wasn’t enough.

“Ain’t nothing to feel good about in a loss,” said veteran swingman Gerald Wallace. “The main thing, you kind of can hold your head up in a loss like this knowing you didn’t play as good as you were supposed to. They made shots. They executed. They did what they were supposed to do to win.”

The Celtics led by 6 in the second quarter but trailed by that many at halftime. An 8-2 run to close the third quarter gave Portland a 90-78 lead entering the fourth.

There were times when the Celtics chipped away, coming within 96-89 after a Sullinger 3-pointer with 8:51 left.

But the Blazers had an answer, as they had all night, and responded with a 7-0 run to lead by 14.

“We were just trading baskets,” Stevens said. “And in a come-back you can’t do that.”

Said Sullinger, “Can’t do much in this league sometimes when a team gets it going. The only thing you can do is pray that the ball don’t go in. Tonight, the ball just seemed like it kept going in every time we tried to make a run.

“We were kind of playing behind the whole game, so when they hit one of those threes it kind of was crushing to us,” Crawford said. “Heads were down a couple of times. Us being a young team, we just got to keep pushing, keep chipping away.”

But, again, the Celtics failed to overcome a late deficit, one that was manageable.

Stevens said that failing to do so again tells him “that we’ve got to get better in the first 42 minutes, to give us a better chance to win it at the end. We weren’t good enough in that time-frame.”

He added that he needed to be fair in his analysis, because credit belonged to the Trail Blazers, a team that has played together for a while, that has go-to options down low in Aldridge and has various options on the perimeter — and that knows where to go when it needs a bucket whenever it needs one.

“Whereas we might be searching a little bit, they know exactly where they need to go, and they did that,” Stevens said.

The Celtics cannot afford to sulk. There’s no time for thatThey play the Timberwolves in Minnesota Saturday, then head to Houston to play the Rockets Tuesday and then to San Antonio to play the Spurs Wednesday.

“We got to win. Got to get a win,” Sullinger said. “That’s the mind-set, and every game is a pride game.”

Late in the game, there were chants of “We Want Wiggins” from some fans at the Garden, a reference to Kansas freshman Andrew Wiggins, who is expected to be a top pick in the 2014 NBA draft.

For them, every loss is not so bad, as it potentially brings them closer to landing the top pick should the Ping-Pong balls land the Celtics’ way.

For Stevens, though, each loss is gut-wrenching, and there seemed to be little he could do to stave off the one that his team earned Friday.

“You know, I hate losing, I don’t stomach it well, I don’t deal with it well,” he said. “But I’ll be back at work tonight.”